collector wasn't starting

[TezkaRabota]

Hi,
I have problem with pg_wait_sampling extension on Postgresql-11.8-1. I want to use it with PoWA, but I get an error: : powa_take_snapshot(0): function "powa_wait_sampling_snapshot" failed: pg_wait_sampling collector wasn't started.
How should I start pg_wait_sampling extension. I installed it using following procedure (on Centos 7):
yum install pg_wait_sampling_11
shared_preload_libraries = 'pg_stat_statements,pg_wait_sampling'
CREATE EXTENSION pg_wait_sampling;

I also try to install last version of extension from scratch, but the result was the same.

Select on pg_wait_sampling_current view gives data. But select on pg_wait_sampling_history and pg_wait_sampling_profile give an error: "ERROR: pg_wait_sampling collector wasn't started
SQL state: XX000".

What am I doing wrong?
Regards

Domen

[TezkaRabota]

Problem solved. Postgresql parameter max_worker_processes was to low.